MILK 227 



Shake with a rotary motion so as thoroughly to mix the acid and milk. 

 Avoid getting curds into the neck of the bottle. 



If the work has been done properly the mixture will be a dark 

 color and very hot. Place directly in a centrifuge, arranging the 

 bottle so that the rotating head will balance properly. If the 

 machine vibrates badly the balance is not correct and should be 

 adjusted. 



Centrifuge for five minutes; then set the bottle in a pan of hot water and 

 add sufficient hot water to bring the fat up to the neck of the bottle. 



Centrifuge for two minutes and add sufficient hot water to bring the fat 

 opposite the graduated scale. 



Centrifuge for one minute, and take the reading from the scale in tenths of 

 1 per cent. 



A pair of small dividers is useful for determining the length of 

 the fat column. This determined, place one leg of the dividers upon 

 zero and take the reading from the opposite leg. It is customary 

 to take the distance from the bottom of the fat column to the top 

 as the true length. 



The fat in milk varies from 2.2 per cent to 9.0 per cent. The 

 United States standard is 3.25 per cent. What is the standard in 

 your State? . 



Mineral Matter in Milk. Milk contains calcium, iron, magne- 

 sium, potassium, sodium, sulphur and phosphorus. All these minerals 

 are essential to the human body. This material is usually spoken 

 of as solids not fat. The average amount of solids not fat in milk 

 should be about 8.2 per cent. 



The old practice* of watering milk has largely disappeared, 

 since the Babcock test so easily determines whether the grade of 

 milk is good or poor. 



An instrument called a lactometer which looks something like a floating 

 thermometer is used to detect the addition, of water. The lactometer deter- 

 mines the specific gravity of the milk; that is, the number of times heavier 

 the milk is than water. The specific gravity of milk varies from 1.029 to 1.035. 

 If water has been added, the specific gravity reads too low. If the fat has 

 been removed, the specific gravity reads too high. If, however, the adulter- 

 ator removed some of the fat and added the correct amount of water, the lac- 

 tometer will show a specific gravity of normal milk. The Babcock test will 

 readily show the condition of the milk. 



